The purpose of square is to provide you with building blocks to create an advanced and maintainable build system so you can streamline your development process and be more productive on a daily basis. In addition to having Node 0.8 installed on your system it might also require sudo privileges for installing the square binary in your /usr/bin directory. I assume that you also have NPM (Node Package Manager) installed together with your Node.js installation. If not, install it as well. It is bundled in the recent node.js version.